Is it permissible to go to the Mormon reading rooms in order
to research my Jewish family roots?

Dear Benjamin,

A few introductory words about the issue. The Mormons have the
largest collection of genealogical data that exists. It is stored
in a structure that is built into a mountain in Salt Lake City,
Utah, and contains information on over two billion people.
This material is also made available via reading rooms located
in cities around the world. The motivation for gathering this
material is that if they have the name of the person, and the
place and date of his death, they can baptize him via proxy.
This means that they will have someone stand in for the deceased
and go through a baptism in his name. The deceased is then given
an opportunity to convert in Heaven (according to their belief.)

Therefore, is it forbidden to approach the Mormons for the purpose
of benefiting from something that is a vehicle for conversion
to their faith?

I asked Rav Chaim Pinchas Scheinberg, shlita, and he said
that it is irrelevant whether or not the genealogical material
is technically a forbidden idolatrous substance. What is relevant
is the fact that the Mormons use this material for conversion
- a purpose akin to idolatrous practices. Therefore, one must
not go to the "Family History Library" in Salt
Lake City, Utah, or to one of their numerous reading rooms.